1. Field of the Invention
The present invention relates to a thin-film piezoelectric element composed of a thin-film piezoelectric material; a thin-film piezoelectric actuator and a thin-film piezoelectric sensor that include the thin-film piezoelectric elements; and a hard disk drive and an ink jet printer apparatus that include the thin-film piezoelectric actuators.
2. Related Background Art
In recent years, there have been advances in practical use of thin-film piezoelectric elements including thin-film piezoelectric materials, instead of bulk piezoelectric materials. Examples thereof include gyroscope sensors, pressure sensors, pulse wave sensors, shock sensors, and microphones, which use a piezoelectric effect, in which a force applied to a piezoelectric film is converted into a voltage; and actuators, ink jet heads, speakers, beepers, and resonators, which use an inverse piezoelectric effect, in which the application of a voltage to a piezoelectric film produces a distortion of the piezoelectric film.
A reduction in the thickness of piezoelectric materials enables the miniaturization of elements and widens the field of application. Furthermore, many elements can be collectively produced on a substrate, thereby increasing the mass productivity. There are many advantages in performance, for example, improvement in sensitivity as a sensor.
In piezoelectric elements, high dielectric loss of piezoelectric materials often causes heat generation and so forth during operation, which is a problem of reliability. In thin-film piezoelectric materials, a material having low dielectric loss comparable to bulk piezoelectric materials are not found. Thus, the design of a piezoelectric thin film having low dielectric loss is an important subject.
Lead zirconate titanate (PZT) is well known as an excellent piezoelectric material. Since it contains lead, alternative (lead-free) materials have been studied in view of the environment and the human body. However, an alternative material having piezoelectric properties comparable to PZT is not found.